A variety of medical imaging technologies have been developed to produce diagnostic images of the interior of the human body. Radiography is frequently used for this purpose, and fluoroscopy is one technology that allows for real time imaging of structures in motion. Fluoroscopic images are formed by measuring the intensity of radiation passing through the patient. The intensity varies with the radiopacity of the imaged region of the patient such that the intensity is representative of the structure of the imaged regions. For fluoroscopic imaging, the intensity of the detected radiation is represented as a visible image. Successive images are captured, each one representing a frame of a video image. Such a video image allows motion of the structures in the region of interest to be observed.
The video image may be displayed in real time or may be recorded and/or played back on a monitor for analysis after it is captured. In some procedures, fluoroscopic imaging is used in real time to aid in the positioning of guidewires or stents in bodily lumens. The guidewire or stent may be built with radiopaque markers to absorb or scatter the majority of x-ray radiation such that when imaged, the markers clearly contrast with relatively radiolucent surroundings. The markers may be placed at strategic positions in the guidewire or stent, such as the distal end, to enable a technician to easily determine the location of the device.
It is also known that a contrast material may be introduced into the patient to delineate anatomy as part of a study using fluoroscopic imaging. The contrast material may reveal functioning of blood vessels, the genitourinary system, or the gastrointestinal (GI) tract, for example. Known contrast materials include barium, in the form of barium sulfate (BaSO4), which may be administered orally or rectally for GI tract evaluation, and iodine in various proprietary forms. These contrast materials absorb or scatter significant amounts of x-ray radiation and may be used with real time imaging to demonstrate dynamic bodily processes.
One such dynamic bodily process that has been observed using radiographic imaging with contrast materials is esophageal peristalsis. Esophageal peristalsis refers to the contraction of circular muscles in the esophagus to propel food and drink through the esophagus to the stomach. For a healthy individual, the contractions begin at the upper end of the esophagus and propagate downwardly toward the lower esophageal sphincter (LES). Though, there are medical conditions under which the normal pattern of contractions is interrupted. This conditions include achalasia, dysphagia, diffuse esophageal spasm, ineffective esophageal motility, and hypertensive LES.